THIS invention relates to a file stiffener, and in particular to a stiffener for ring binder and lever arch-type files.
Unless ring binder and lever arch-type files are filled to their capacity, the opposed file covers are inclined towards one another, with the result that, when viewed from above, the file has a triangular or trapezoidal profile. Partly filled files cannot be newly or efficiently stacked together when the spine width is greater than the gap between the free ends of the file cover. Additionally, because file covers are typically open and unsupported on three sides, asymmetrical acute and obtuse angles are defined between the file covers and the spine, so that the covers are not held uniformly at right angles to the spine. This in turn leads to a tendency for the files to tilt sideways and ultimately to deform. Yet another notable disadvantage of conventional lever arch files, is that their design is such that all the weight of the filed contents is supported by only one of the opposing file covers. As the contents get heavier, the vertical shear moment on the opposing file covers become progressively imbalanced, further contributing to instability and distortion of the file.
The rigid parallelepipedal structure of box files avoids the stacking and stability problem which arises with lever arch files. Box files are generally more expensive as well as being more cumbersome and bulky than lever arch files which are capable of accommodating a similar volume of documentation, and they are less convergent to use.